The purpose of this study is to compare the efficacy of benazepril, a new ACE inhibitor from CIBA-GEIGY, given once a day in salt-sensitive vs. non salt- sensitive essential hypertensive patients. We are comparing the effects of placebo and benazepril using 24 h. ambulatory blood pressure monitoring and renal blood flow measurements. The hypothesis is that an ACE inhibitor will be particularly effective in the salt-sensitive population.